I would not advise staying here unless you are comfortable with trespassing and the risk of prosecution. It appears the unit is being rented out in violation of the building's policies.
My check-in instructions from the host were shady ("Do not contact property security and reception")
I arrived in the evening and found the following sign in the elevator after collecting my key from the host's mailbox:
DAILY AND WEEKLY RENTALS ARE AGAINST THE HOTEL ACT, IMMIGRATION ACT, AND BUILDING CONTROL ACT. OFFENDERS WILL BE PROSECUTED BY LAW.
IF YOU SUSPECT ANY RESIDENTS ARE VIOLATING THIS RULE, OR IF YOU ARE A TRAVELER WHO IS UNFAMILIAR WITH THAI LAW, PLEASE VISIT THE JURISITIC OFFICE OR CONTACT MANAGEMENT AT [PHONE NUMBER]. OFFENDERS WHO DO NOT DECLARE THEIR ACTIVITY WILL BE REPORTED TO THE POLICE AS TRESPASSERS AND PROSECUTED UNDER THAIL LAW AND HAVE TO PAI FOR THE FINE 2500, 5000, AND 10000 THAI BATH [sic.]